Long but very thoughtful process, good communication until the end, need to have better followup with rejected candidates, consider shortening process.
Stages are the same as other interviewers mentioned here - contacted by a recruiter, an initial screen, a technical screen (conversation, not coding), a take-home (recommend 4-8 hours, depends on how polished you want it to be. I spent on the longer side and still got questions about why I didn't implement more advanced JS bling, etc), a review of the take home, an on-site (6 interviews back to back, though many of those were remote from their office - mostly culture/communication interviews, and technical architecture questions, no gotchya algorithm type questions), reference check, founder interview
I found the process laid out pretty clearly and moved fairly quickly all the way through, though communication was often very terse (I was asked to fly out to SF in less than a week's time, but still had to follow up to figure out how I handled booking logistics, etc and didn't hear back until late Friday night when needed to be in SF on Sunday night). But everything was kind and clear.
I found the interviews greatly geared towards conversation and thoughtful dialog - indeed the demeanor of the interviewers was what attracted me to the company. One interviewer was very new to the company and did not seem as thoughtful and was pretty clearly biased against my non-traditional background and kept emphasizing in various ways that this was a lot of Silicon Valley venture capital propelling a fast-moving startup culture and that he didn't know if I was ready to be pushed so hard, which was a bit eye-rolly, but he was definitely the exception to the rule of kind and thoughtful communicators.
Process moved quick until the end when it dragged out a bunch - was clear that it was a slow-roll while some sort of decision was being made, but communication was few and far between for last two weeks or so (after being very fast about scheduling next steps, it was a very noticable slowdown)
Even though I had talked to some of the same people for over 2 hours, and had a recruiting contact, final rejection was a one sentence email from a stranger. Request for any follow-up evaluation or feedback was ignored (which seems par for the course in SV these days, but still sucks).
They also have you take a personality test, and they do give you a print-out of the results, but no one ever mentioned it or discussed it in any way.
Overall, it's clear this company /really/ cares about their culture and what they are doing, and they have an intentional interview process. Personally I find asking candidates to spend 20/30/40 hours in an unpaid interview process while working their full-time job to be a bit extreme, but you know what you are getting into. At least 3-4 hours of remote interviews, at least 4-8 hours of take-home work, at least a day of on-site interviews, and travel time.
My suggestion would be that if you are serious about your humans first and employees second culture, to extend that to "humans first/applicants second" as well. People are investing a tremendous amount of energy in an interview process that actually is geared towards pretty intense vulnerability about their hopes / dreams / fears / weaknesses etc.
One line rejection emails may be cost-effective, but if you are invested enough in the entire hiring process, invest some in the candidate feedback process as well.